Carbohydrates Flashcards
Which two types of sugars are considered “simple”
- monosaccharides
- disaccharides
Which two types of sugars are considered complex sugars?
- oligosaccharides
- polysaccharides
Disaccharides are two monosaccharides joined by a(n) ________ bond
acetyl (glycosidic)
What is the ratio of H:O in CHOs
2:1
Which monosaccharide is nutritionally the most important? Trioses, Pentoses or Hexoses
Hexoses
What is a chiral carbon?
a carbon with four different groups attached to it
What is the difference between D and L sugars
D - last OH is on the right side of the chain
L - last OH is on the left side of the chain
Are D or L sugars more nutritionally important? Why?
D because digestive enzymes are stereospecific for D sugars
Which of the three common disaccharides is/are reducing sugars? (sucrose, lactose and maltose)
- lactose
- maltose
Which of the three common disaccharides is/are non-reducing sugars? (sucrose, lactose and maltose)
sucrose
what is the minimum amount of monosaccharides required to be considered a polysaccharide
6
are hetero or homopolysaccharides more abundant in food?
homopolysaccharides
What are three types of insoluble dietary fibres?
1.Cellulose
2.Hemicellulose
3.Lignin
What are three types of soluble dietary fibres
- Pectin
- Gums
- Mucilages
This dietary fibre has B-1,4 glucose units
Cellulose
This dietary fibre has a mixture of a and b glycosidic linkages
hemicellulose
this dietary fibre has a-1,4-linked-D galacturonic acid backbone
Pectin
What is the function of insoluble fibre?
- decreases constipation
- stimulates muscle contraction to break down waste
- decreases risk of bacterial infections
What is the function of soluble fibre?
- increase satiety
- delays gastric emptying
- slows nutrient uptake
What types of bonds does salivary a-amylase break down? What is resistant?
- breaks down a-1,4-glycosidic bonds
- cellulose, lactose, and a-1,6-bonds are resistant
what does isomaltase do?
breaks a-1,6 glycosidic bonds that are resistant to stomach and salivary digestion. (into 2 glucose)
What are most monosaccharides taken up by?
enterocytes
What types of sugars enter the blood by basolateral GLUT2?
glucose, galactose and fructose
What are the three fates that glucose has in a cell?
- enter glycogenesis for energy storage
- enter glycolysis for energy production
- enter hexose monophosphate shunt to generate precursors for biogenesis
What is the function of the Glycogen Synthase enzyme?
- converts glucose 1-phosphate to glycogen
what is the function of the glucokinase enzyme in the liver?
- convert blood glucose to glucose 6-phosphate
what is the function of the glycogen phosphorylase enzyme?
- break down glycogen to glucose 1-phosphate by breaking a-1,4-glycosidic bonds
What is the function of the hexokinase enzyme?
- Converts blood glucose to glucose 6-phosphate in muscle
What is the function of the glucose-6-phosphatase enzyme?
- convert glucose 6-phosphate to blood glucose in the liver
what does glucagon stimulate??
glycogen breakdown
what does insulin do?
- stimulates glycogen formation
- stimulates glucose uptake from food into tissue cells
What does low blood sugar stimulate?
glucagon release
what does high blood sugar stimulate?
insulin release
what is the net energy yield from one glucose in glycolysis
- 2 NADH
- 2 ATP
(8 ATP)
What is the Cori cycle?
- occurs under anaerobic conditions in muscle leading to the production of lactate
- lactate gets transported back to the liver and converted to pyruvate
- gluconeogenesis allows for conversion of pyruvate back to glucose
- not sustainable because 6 ATP is required for 2 molecules of lactate to form glucose
What does the hexose monophosphate shunt do>
generation of NADPH and precursors for nucleotide synthesis
What vitamins are used as cofactors in the pyruvate dehydrogenase complex
- thiamine
- niacin
- riboflavin
- pantothenic acid
How much ATP is generated from 1 NADH
3
How much ATP is generated from 1 FADH2
2
How much ATP is generated from one GTP
1
What is the energy yield from one acetyl-coA in the Kreb’s cycle
- 3 NADH
- 1 FADH2
- 1 GTP
(12 ATP)
What is the energy yield from pyruvate dehydrogenase?
1 NADH
What is the ATP yield from the complete oxidation of 1 mole of glucose?
- 38 ATP
- Glycolysis = 2 NADH (6 ATP) + 2 ATP
- Pyruvate Dehydrogenase = 1 NADH (3 ATP)
- Kreb’s cycle = 3 NADH (6 ATP), 1 FADH2 (2 ATP), 1 GTP (1 ATP) x 2 because 2 acetyl coA